This invention relates to the field of retroreflectors, and more particularly, to lateral transfer retroreflectors.
Retroreflectors generally have the property of causing incident and reflected light rays to travel along parallel paths. To achieve this parallelism, a retroreflector normally consists of three optically flat reflecting surfaces, each reflecting surface positioned at a right angle to each of the other reflecting surfaces. Any departure of the reflecting surfaces from their perpendicular orientation will cause the incident and reflected light rays to depart from parallel.
Retroreflectors lose accuracy when they are exposed to external stresses. Examples of such external stresses are mass, thermal expansion or contraction of the substrate material from which the retroreflector is made, or deflection caused by curing of the adhesives which join members of the retroreflector.
Retroreflectors, and lateral transfer retroreflectors (which translate the reflected beam some calculated distance from the incident light beam), are old in the art. Examples of prior art retroreflectors and lateral transfer retroreflectors are:
U.S. Pat. No. 3,977,765 to Morton S. Lipkins, which disclosed a retroreflector mounted to a support structure through means of applying an adhesive into the joints formed between joined members of the retroreflector and to a flat surface of the support structure.
U.S. Pat. No. 4,065,204, also to Morton S. Lipkins, which disclosed a lateral transfer retroreflector consisting of a base, a roof reflector having two reflecting plates and a third reflector. The base acts as an extension of the third reflector by attaching the third reflector to the roof reflector in the manner known to retroreflectors to produce the lateral transfer retroreflector construction.
U.S. Pat. No. 5,024,514 to Zvi Bleier and Morton S. Lipkins, which discloses a lateral transfer retroreflector having a tubular member, a roof mirror and a mirror panel. Both the roof mirror and mirror panel are attached to the tubular member by use of three coplanar mounting pads.
U.S. Pat. No. 5,361,171, also to Zvi Bleier, which discloses a lateral transfer retroreflector having a fixed-length tubular member, a roof mirror secured within a channel portion extending from an end of the tubular member and a mirror panel attached to the tubular member at the opposite end from the roof mirror and roof mirror panel.
It would be desirable to provide a high-accuracy lateral transfer retroreflector that is off-the-shelf adjustable as to the displaced length between the mirror panel and the roof mirror and also having a less temperature-deviant assembly and mounting of the roof mirror and mirror panel.
In accordance with the invention, an improved lateral transfer retroreflector assembly is provided. The lateral transfer retroreflector assembly of the invention is comprised of three separate, attached segments. A first segment comprising a mirror panel housing, a second segment comprising a roof mirror housing, and a third segment comprising a connecting member between the two housings.
The mirror panel housing will have mounted thereto a mirror panel. The roof mirror housing will have mounted thereto a roof mirror assembly, and the connecting member will be mounted between the mirror panel housing and the roof mirror housing. In addition, based upon the mounting together of the three separate segments, the connecting member will have the ability of being an off-the-shelf member that is selectively able to be cut to a particular length dimension based upon customer specifications, thereby allowing for customized creation of lateral transfer retroreflectors, but at a time and cost savings to the customer.
In addition, the roof mirror assembly and the mirror panel mounting are kinematic structures that are also improvements over earlier constructions. In particular, the roof mirror assembly of the subject invention has at least a pair of mounting members that act also as back supports and are located substantially at opposite ends of the roof mirror. The manner of attachment of the mounting members to the back portions of the mirror panels making up the roof mirror assembly, is such that expansion and contraction of the reflective surfaces of the mirror panels of the roof mirror assembly will only be in a direction substantially perpendicular to the direction of the roof angle axis. Deflection in this direction does not cause displacement (error), of the transmitted light beam traveling through the lateral transfer retroreflector, and therefore such a mounting system is advantageous. Similarly, the mounting of the mirror panel to the mirror panel housing by means of substantially 45xc2x0 chamfered edges, insures that the forces exerted by thermal expansion or contraction of the bonding material situated along those chamfered edges, will have a canceling effect, and not deflect the reflective surface of the mirror panel.
Accordingly, it is an object of the present invention to provide an improved lateral transfer retroreflector assembly.
Still another object of the invention is to provide a lateral transfer retroreflector assembly having a component construction capable of, allowing for off-the-shelf customization for different customer needs based upon differing customer specifications.
Yet a further object of the invention is to provide a lateral transfer retroreflector assembly having a roof mirror assembly construction and mounting such that deformations in the reflective surfaces of the mirror panels of the roof mirror assembly due to thermal expansion/contraction are minimized in the direction of the roof angle axis.
A still further object of the invention is to provide a lateral transfer retroreflector assembly, wherein the deflective forces exerted on the mirror panel by thermal expansion or contraction of the joint bonding the mirror panel to the mirror panel housing, are minimized.
Other objects of the invention will in part be obvious and will in part be apparent from the following description taken in association with the figures.
The invention accordingly comprises an assembly possessing the features, properties and relation of components which will be exemplified in the products hereinafter described, and the scope of the invention will be indicated in the claims.